This invention relates generally to specific fabric articles exhibiting very low air and/or gas permeability (even upon application of high inflation pressures) and very high tear strengths. Such a specific fabric also permits the incorporation of discrete openings (through cutting, for example) through which air and/or gas introduced by an airbag inflation canister will travel. Such a specific fabric acts as a barrier to the complete introduction of high pressure inflation gases into an airbag cushion, thereby permitting a more controlled, safer inflation upon the occurrence of a collision event. Thus, the specific inventive fabric permits movement of inflation gas and/or air substantially solely through the incorporated openings within the fabric and not through the interstices between the individual fiber constituents. The inventive fabric also withstands the intense heat generated by the explosion that creates the inflation gases and does not lose any appreciable degree of performance during and after such an inflation event. An inflation module, as well as an entire vehicle restraint system, comprising such a specific timing fabric are also contemplated within this invention.
All U.S. patents cited herein are hereby fully incorporated by reference.
Inflatable protective cushions used in passenger vehicles are a component of relatively complex passive restraint systems. The main elements of these systems are: an impact sensing system, an ignition system, a propellant material, an attachment device, a system enclosure, and an inflatable protective cushion. Upon sensing an impact, the propellant is ignited causing an explosive release of gases filing the cushion to a deployed state which can absorb the impact of the forward movement of a body and dissipate its energy by means of rapid venting of the gas. The entire sequence of events occurs within about 30 milliseconds. In the undeployed state, the cushion is stored in or near the steering column, the dashboard, in a door, in the roof line or roof rail, or in the back of a front seat placing the cushion in close proximity to the person or object it is to protect.
Inflatable cushion systems commonly referred to as air bag systems have been used in the past to protect both the operator of the vehicle and passengers. Systems for the protection of the vehicle operator have typically been mounted in the steering column of the vehicle and have utilized cushion constructions directly deployable towards the driver. These driver-side cushions are typically of a relatively simple configuration in that they function over a fairly small well-defined area between the driver and the steering column. One such configuration is disclosed in U.S. Pat. No. 5,533,755 to Nelsen et al., issued Jul. 9, 1996, the teachings of which are incorporated herein by reference.
Inflatable cushions for use in the protection of passengers against frontal or side impacts must generally have a more complex configuration since the position of a vehicle passenger may not be well defined and greater distance may exist between the passenger and the surface of the vehicle against which that passenger might be thrown in the event of a collision. Prior cushions for use in such environments are disclosed in U.S. Pat. No. 5,520,416 to Bishop; U.S. Pat. No. 5,454,594 to Krickl; U.S. Pat. No. 5,423,273 to Hawthorn et al.; U.S. Pat. No. 5,316,337 to Yamaji et al.; U.S. Pat. No. 5,310,216 to Wehner et al.; U.S. Pat. No. 5,090,729 to Watanabe; U.S. Pat. No. 5,087,071 to Wallner et al.; U.S. Pat. No. 4,944,529 to Backhaus; and U.S. Pat. No. 3,792,873 to Buchner et al.
The majority of commercially used restraint cushions are formed of woven fabric materials utilizing multifilament synthetic yarns of materials such as polyester, nylon 6 or nylon 6,6 polymers. Representative fabrics for such use are disclosed in U.S. Pat. No. 4,921,735 to Bloch; U.S. Pat. No. 5,093,163 to Krummheuer et al.; U.S. Pat. No. 5,110,666 to Menzel et al.; U.S. Pat. No. 5,236,775 to Swoboda et al.; U.S. Pat. No. 5,277,230 to Sollars, Jr.; U.S. Pat. No. 5,356,680 to Krummheuer et al.; U.S. Pat. No. 5,477,890 to Krummheuer et al.; U.S. Pat. No. 5,508,073 to Krummheuer et al.; U.S. Pat. No. 5,503,197 to Bower et al.; and U.S. Pat. No. 5,704,402 to Bowen et al. A two-weave construction airbag cushion is exemplified in U.S. Pat. No. 5,651,395 to Graham et al. but does not discuss the importance of narrow basket-weave single fabric layers.
As will be appreciated, the permeability of an airbag cushion structure is an important factor in determining the rate of inflation and subsequent rapid deflation following the impact event. Different airbag cushions are utilized for different purposes. For instance, some airbag cushions are installed within inflation modules for driver protection within the steering column of an automobile. Others are utilized as protection for front seat passengers and are installed in and around the glove compartment and/or on the dashboard in front of such a passenger seat. Still others have been developed in an effort to protect all passengers during a long-duration impact event, such as, for example, a rollover collision. In those types of crashes, the target airbag cushion must inflate quickly under high pressure (such as between about 10 and 40 psi) and remain inflated at a relatively high pressures in order to provide the greatest degree of protection to such passengers. Furthermore, such long-duration airbag cushions preferably comprise xe2x80x9cpillowxe2x80x9d formations created through the attachment of at least two different fabrics or fabric ends together and sealed, sewn, or the like, together. Upon inflation the free space between the attachment points inflate as well, thereby producing the desired cushioned xe2x80x9cpillowxe2x80x9d structures. Such long-duration, xe2x80x9cpillowedxe2x80x9d structures have been disclosed in the prior art as airbag cushions within U.S. Pat. No. 5,788,270 to Halano as well as within U.S. patent application Ser. No. 09/406,264 to Sollars, Jr., now U.S. Pat. No. 6,220,309.
Generally, recent airbag improvements have involved various types of alterations to either the bag structures and/or coatings, or, most importantly for this invention, the inflators and propellants utilized to provide more effective and safer supplemental vehicle restraint systems. In the past, the standard inflators produced extremely hot and potentially destructive explosions during propellant ignition to effectively and quickly (e.g., in less than 0.2 milliseconds) introduce sufficient amounts of inflation gas into the desired airbag to protect a passenger or driver during a collision. In recent years, more controlled and safer inflation modules have been developed which still provide highly effective inflations as needed. However, some drawbacks have resulted, particularly within and for larger airbag which require long-term, sustained inflation (such as side curtain-type airbags). Most notably, such airbags must be inflated at an even rate to provide the most efficient and effective protection to the vehicle occupants. The xe2x80x9cpillowedxe2x80x9d structures within the target side curtain airbags thus need a relatively similar inflation pattern. Since most inflators for such airbags have been developed to inflate from a single small area and force inflation gas to portions of the target airbags at differing distances from the point of ignition, controlled inflation at similar speeds have been extremely difficult. New developments, such as that disclosed within European Patent Application 0,995,645 A2 to OEA, Inc. have provided highly desirable procedures and apparati to inflate such side curtain airbags in more efficient and effective manners. In this specific Application, the ignited propellant is forced into an inflation manifold (for example, a rubber tube) located in the roofline of the vehicle. This manifold comprises openings at selected locations which permit passage of certain limited amounts of inflation gas to eventually enter and inflate the target airbag, particularly within the specific xe2x80x9cpillowedxe2x80x9d structures, on an even basis. However, even with this system in place, there still exists a need to control the limited amounts of inflation gas in order to assure a controlled and effective airbag inflation. Thus, there is also taught the addition and use of a timing member, such as a plastic or metal, which itself comprises openings corresponding to those present within the inflation manifold. This metal or plastic timing member is preferably present in a tube shape as well and will inflate to a very low degree, if at all, upon entry of the inflation gas from the inflation manifold. However, inflation gas will also be forced through the openings within the timing member and then into the airbag for inflation. Although the actual time of inflation is incredibly fast (again, no more than about 0.2 milliseconds), the ability to provide controlled and even inflation, as well as to better ensure the airbag does not overinflate or inflate too quickly is paramount to providing a safe and effective supplemental vehicle restraint system of this type. Without such a timing member, the controlled inflation would be extremely difficult if not impossible due to the incredible, yet necessary, force produced upon ignition of the propellants in order to actually provide the quick inflation of the target airbag.
Furthermore, with regard to this OEA, Inc. European Patent Application, high temperature inflation gases are generated during the propellant ignition, both as a result of such an explosion and in order to assure full inflation of the target airbag. If the inflation is too cool in temperature, the gases will not expand sufficiently and thus the target airbag will not fully inflate. Thus, it is, as noted above, extremely important to permit sufficient, though not too much, inflation gases to pass through the openings within the metal or plastic timing member. The passage of too much inflation gas (through, for example, weak or damaged areas within the timing member) would actually cool the inflation gas and prevent the desired degree of airbag inflation. However, there is also a problem with such excessive generated heat in that the target airbag may conduct such heat to the vehicle occupant. Such problems may be alleviated by the application of exterior and/or interior coatings to the target airbag; however, the presence and utilization of the metal or plastic timing member aids in this instance as well.
Although such a timing member has been taught in the past as a desired component within such new airbag inflation systems, there have no teachings concerning fabrics utilized as timing members with any such high pressure inflation assemblies. Fabrics are most highly desired for such a purpose due to costs, ease of manufacture, foldability, unfoldability (upon inflation), lower weight, and many other reasons. Such a practice of fabric timing members has been limited, if not impossible, due to the difficulties in developing a proper fabric for this specific purpose. Again, the fabric must be able to withstand extremely high pressures and tensile forces during inflation, excessive heat during inflation, and must effectively permit the vast majority of inflation gas to escape through the provided openings which correspond to the inflation manifold openings, and thus must exhibit extremely low air and gas permeabilities in the remaining portions of its constituent fabric. Furthermore, since such a timing member will be folded during storage for an indefinite amount of time prior to use, it must also exhibit extremely good blocking characteristics such that the fabric portions do not adhere together in a deleterious manner such that upon inflation the timing member does not unfold properly and thus does not function as needed. There have been no teachings or developments of such fabric timing member meetings all of these objectives to date within the pertinent prior art. Thus, there is a perceived need to provide such an effective fabric timing member in order to make available to the airbag industry these new, safe, and highly effective inflation modules.
In light of the background above, it can be readily seen that there exists a need for an effective fabric timing member for utilization within such specific airbag inflation assemblies having inflation manifolds for the transport of inflation gas from the propellant ignition location ultimately into the target airbag article. The reasons for utilizing a fabric for such a timing member include, without limitation, the ability to expand and unfold (and thus the ability to fold and pack well within the inflation assembly itself) upon inflation, the low costs involved with producing fabrics as opposed to other inflation articles (including metal articles), lighter weight inflation assemblies, reduction of complex parts within the inflation assembly, simplification of inflator design and function, and adaptability of such an inflation assembly to multiple inflation applications. Furthermore, in furtherance of these objectives, such a fabric permits the ability to provide strength to specific areas of the timing member through weave formations or insertions of extra threads, and the ability to control (preferably lower and eliminate, if possible) the air permeability of the timing member through the application of coating compositions to the surfaces thereof. Thus, although alternative articles and structures may provide some of the characteristics necessary for proper functioning within an inflation assembly as described above, in short, the utilization of fabrics for this purpose is most highly desired.
Such fabric utilization within an inflation assembly timing member has been rather difficult to achieve until now, unfortunately. It is true that fabrics have been utilized as the primary constituents within airbags themselves (which must withstand heat and high inflation pressures); however, such fabrics have not proven useful and/or workable as timing members. Traditional airbag fabrics are structured to either permit quick inflation and then quick deflation (such as within driver and front-seat passenger side airbags, and also certain non-rollover protection side curtains) or long-term inflation (to protect in rollover situations, such as the side curtain-type airbags discussed above). As such, the fabrics utilized are not conducive to actually acting in a controlling fashion for extremely high pressure and high temperature inflation gases. The tensile strengths exhibited by these traditional airbag fabrics do not exceed 400 pounds per square inch (or about 675 newtons per centimeter). The timing member must exhibit a far greater tensile strength on the order of at least about 900 lb/inch in the warp direction (preferably between about 950 and 1,500 lb/inch, more preferably between about 1,000 and 1,250 lb/inch, and most preferably from about 1,000 to about 1,100 lb/inch) and at least 700 lb/inch in the fill direction (preferably between about 750 and 1,200 lb/inch, more preferably between about 800 and 1,000 lb/inch, and most preferably between about 800 and 900 lb/inch). Furthermore, the high temperatures withstood by the traditional airbag fabrics are generally much lower than those required of such a timing member (due to the location of the entire timing member in relation to the actual point of propellant ignition as compared with an airbag cushion). Thus, it is evident that although airbag fabrics have been developed in the past to withstand certain high inflation pressures and temperatures, such fabrics do not function properly as timing members within the new inflation assemblies (as discussed above) due to the pressures and temperatures which exceed such limits.
Other fabrics have been developed as filter fabrics for airbags, such as in U.S. Pat. No. 5,441,798 to Nishimura et al., which permit control of inflation to prevent too rapid and excessive airbag expansion upon ignition of a propellant. However, such filter cloths and fabrics do not include specific openings through which substantially all of the inflation gasses are transported into the target airbag. In fact, the fabrics discussed and disclosed by patentee actually exhibit relatively high air and/or gas permeabilities as opposed to the required low permeabilities exhibited by the inventive timing member. Due to such high permeability characteristics, the tensile strength of the patented filter cloth within Nishimura et al. is apparently relatively low (on the magnitude of standard airbag fabrics themselves) which thus, again, would prevent utilization of such a patented filter cloth as a timing member within the inflation assemblies discussed above.
As such, it is an object of this invention to provide a fabric for proper functioning as a timing member for a high pressure inflation assembly comprising an extended inflation gas manifold. A further objective is to provide a relatively inexpensive high tensile strength, low air and/or gas permeability timing fabric for controlled inflation of an airbag cushion.
Accordingly, this invention is directed to an airbag inflation assembly timing member comprising discrete openings in relation to preselected locations for introduction of inflation gas within a target airbag;
wherein said timing member comprises a fabric;
wherein a coating has been applied to at least a portion of said fabric; and
wherein said timing member exhibits (a) an average overall tensile strength of at least 900 lb/inch in the warp direction and an average overall tensile strength of at 700 lb/inch, both up to a temperature of at least 80xc2x0 C., (b) a permeability to air of at most 0.07 cfm at 125 Pa and of at most 0.3 cfm at 2,500 Pa, and (c) no appreciable blocking upon inflation upon storage in an environment heated to about 100xc2x0 C. for 7 days.